The vulnerability is tracked as CVE-2018-5440 and it has been assigned a CVSS score of 9.8, and the worst news is that it is quite easy to exploit.

The WebVisu product is currently used in 116 PLCs and HMIs from many vendors, including Schneider Electric, Hitachi, Advantech, Berghof Automation, Hans Turck, and NEXCOM.

An attacker can remotely trigger the flaw to cause a denial-of-service (DoS) condition and under some conditions execute arbitrary code on the web server.

“A crafted request may cause a buffer overflow and could therefore execute arbitrary code on the web server or lead to a denial-of-service condition due to a crash in the web server. ” reads the security advisory issued by CODESYS.

According to CODESYS, there is no evidence that the flaw has been exploited in the wild.

The flaw affects all Microsoft Windows (also WinCE) based CODESYS V2.3 web servers running stand-alone or as part of the CODESYS runtime system prior version V1.1.9.19.

The company has released the CODESYS web server V.1.1.9.19 for CODESYS V2.3 to
address the flaw. This is also part of the CODESYS setup V2.3.9.56.

The vendor also recommends organizations to restrict access to controllers, use firewalls to control the accesses and VPNs.

In December 2017, security researchers at SEC Consult discovered a flaw in version 2.4.7.0 of the CODESYS runtime which is included on PFC200s with firmware version 02.07.07. The CODESYS runtime is commonly included on PLCs to allow for easy programming by users. 17 models of WAGO PFC200 Series PLC were found vulnerable to remote exploit.

A PLC flaw can be a serious threat to production and critical infrastructure

Back to the present, querying the Shodan search engine for port 2455 used by CODESYS protocol we can find more than 5,600 systems are exposed online, most of them in the United States, Germany, Turkey, and China.

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Pierluigi Paganini is member of the ENISA (European Union Agency for Network and Information Security) Threat Landscape Stakeholder Group and Cyber G7 Group, he is also a Security Evangelist, Security Analyst and Freelance Writer.
Editor-in-Chief at "Cyber Defense Magazine", Pierluigi is a cyber security expert with over 20 years experience in the field, he is Certified Ethical Hacker at EC Council in London. The passion for writing and a strong belief that security is founded on sharing and awareness led Pierluigi to find the security blog "Security Affairs" recently named a Top National Security Resource for US.
Pierluigi is a member of the "The Hacker News" team and he is a writer for some major publications in the field such as Cyber War Zone, ICTTF, Infosec Island, Infosec Institute, The Hacker News Magazine and for many other Security magazines.
Author of the Books "The Deep Dark Web" and “Digital Virtual Currency and Bitcoin”.